This research project is concerned with the viscoelastic behavior of mammalian cell DNA. We are examining the conformational properties of mammalian DNA from cells that have been treated with gamma-rays and various drugs in an effort to characterize the DNA damage resulting from such treatment. Repair of the various lesions introduced by gamma-rays and drugs is also being investigated. The types of damage under study include single-strand and double-strand breaks and DNA-DNA crosslinks.